Which statement about the initial nucleotide strand is true?

Which statement about the initial nucleotide strand is true?

• A. It is the RNA primer
• B. It is the leading DNA strand
• C. It is an Okazaki fragment
• D. It is a template for transcription

Answer: (A)

The initial nucleotide strand is an RNA primer. DNA polymerase cannot start a new DNA strand from scratch; it needs a 3' hydroxyl to add nucleotides. Primase lays down a short RNA sequence complementary to the template, providing that 3' end for DNA polymerase to extend. This primer is used to begin synthesis on both strands—the leading strand is extended continuously from its primer, while the lagging strand starts a new primer for each Okazaki fragment. After synthesis, the RNA primer is removed and replaced with DNA. The other statements don’t fit because the leading strand is DNA, not the initial RNA primer; Okazaki fragments are DNA pieces, not primers; and transcription uses a DNA template to make RNA, not a primer used for DNA replication.

The initial nucleotide strand is an RNA primer. DNA polymerase cannot start a new DNA strand from scratch; it needs a 3' hydroxyl to add nucleotides. Primase lays down a short RNA sequence complementary to the template, providing that 3' end for DNA polymerase to extend. This primer is used to begin synthesis on both strands—the leading strand is extended continuously from its primer, while the lagging strand starts a new primer for each Okazaki fragment. After synthesis, the RNA primer is removed and replaced with DNA. The other statements don’t fit because the leading strand is DNA, not the initial RNA primer; Okazaki fragments are DNA pieces, not primers; and transcription uses a DNA template to make RNA, not a primer used for DNA replication.